1. Field of the Invention
The present invention generally relates to an apparatus for fabricating a semiconductor device and, more particularly, to an apparatus for individually separating semiconductor chips formed on a semiconductor wafer.
2. Description of the Prior Art
A technique for individually separating a plurality of chips formed on a single wafer is called "dicing". As a separating method, there are two systems; a scribing system in which the wafer is scribed along the chips to form scribed grooves with the use of a laser or a diamond needle and the chips are subsequently mechanically separated, and a dicing saw system in which the high speed rotation of a thin diamond blade is used to cut deep so that the chips can be mechanically separated or to render the chips to be separable during the cutting.
The wafer half-cut by use of either the scribing technique or the dicing technique is divided into the individual chips by a mechanical means. FIG. 5 illustrates a schematic construction of one prior art apparatus for dividing the wafer.
The apparatus shown in FIG. 5 comprises a base 1 having a rubber mat 2 placed thereabove. A half-cut wafer 3 having first and second surfaces opposite to each other and having chips formed on the first surface thereof is placed on the rubber mat 2 with the first and second surfaces thereof confronting the rubber mat 2 and upwardly, respectively. Prior to the placement of the wafer 3 on the rubber mat, an adhesive tape 5 is applied to the second surface of the wafer so that, when the wafer 3 is divided or separated, the chips will not scatter and can be retained in position.
While a peripheral surface of a generally cylindrical rod-like roller 14 is pressed against the second surface of the wafer 3, the roller 14 is driven to rotate about the longitudinal axis thereof to separate the wafer 3. The chips divided from the wafer are separated on the tape 5 and are suitably cut according to the need for actual use.
As hereinabove discussed, the prior art apparatus for dividing the chips formed on the generally circular wafer is so designed that the wafer supported by the rubber mat having high elasticity placed on the base is divided while the cylindrical rod-like roller is pressed thereagainst. Both of the wafer and the rubber mat when pressed by the cylindrical rod-like roller are downwardly loaded to deform. Because of this, the wafer can be cut only in one direction and, in order for the wafer which has been scribed to be cut in both X-axis and Y-axis directions, the process must to be repeated two times.
Moreover, while a pressing surface exhibited by the rotation of the cylindrical rod-like roller is flat, a peripheral area of the wafer may have a film such as SiN film left unremoved, rendering the peripheral area of the wafer thicker than the remainder thereof. Therefore, a greater pressing force acts on the peripheral area of the wafer than on a central area thereof.
Furthermore, according to the prior art apparatus, localized areas of the wafer tend to be excessively pressed to such an extent as to result in breakage of the wafer and/or damages to the wirings fabricated on the wafer. In order to avoid these problems, the adjustment of the pressing force is required, rendering the apparatus as a whole costly to manufacture. In addition, subsequent to the separation of the chips, the adhesive tape must be expanded to separate the chips individually, requiring increased manufacturing steps.